He warned the defendants: "If you fail to meet any aspect of the order you will serve a term of imprisonment."

Criminal action was taken in tandem with civil litigation to secure a ban on the trader selling any NPS from Soho Bookshop.

An interim order, imposed by Mr Justice Deeny at the High Court last November, was granted under the General Product Safety Regulations.

Attorney General John Larkin QC and the City Council jointly sought the prohibition against Brown, Campbell, Bradshaw and a fourth defendant named Aiden Kerr - now believed to be fictitious.

Under its terms the defendants are prohibited from selling NPS anywhere in Northern Ireland.

Belfast City Council welcomed the landmark legal ruling and a spokesperson said: “We are delighted that these individuals can no longer supply Novel Psychoactive Substances, otherwise known as ‘legal highs’. These substances don’t meet the necessary safety requirements; just because they are not banned under drugs laws does not mean that these substances are safe. They are a risk to a user’s health because their production is not regulated and the consumer simply can’t be certain as to what is in them and their potential harmful effects.

“As a result of Belfast City Council’s work there are no longer any shops in the Belfast City Council area selling Novel Psychoactive Substances. They can however be bought from other sources and Belfast City Council is continuing to work in partnership with the PSNI, the Attorney General for Northern Ireland and others to do everything possible to tackle this ongoing scourge.”